The present invention relates to a method and apparatus for inspecting a defect present on the top and edge surfaces of a sample such as a semiconductor substrate and a thin film substrate with high sensitivity and at high speed.
In a production line for a semiconductor substrate or for a thin film substrate, an inspection operation is performed to inspect a defect on the surface of the semiconductor substrate or on the surface of the thin film substrate in order to maintain or improve the yield of products.
As a conventional method and apparatus for inspecting a defect, JP-A-H09-304289 (Patent Document 1), JP-A-2003-240730 (Patent Document 2) and JP-A-2008-32621 (Patent Document 3) are known.
Patent Document 1 discloses an apparatus for inspecting the surface of a wafer. The apparatus described in Patent Document 1 has a low-angle optical receiver and a high-angle optical receiver. The low-angle optical receiver is located such that it forms an elevation angle of 30 degrees or less with respect to the surface of the wafer, while the high-angle optical receiver is located such that it forms an elevation angle of more than 30 degrees with respect to the surface of the wafer. The apparatus uses a laser beam to scan the wafer. Each of the low-angle and high angle optical receivers receives light scattered from the wafer illuminated with the laser beam to detect a foreign material by means of the scanning. The foreign material detected from a certain area of the wafer by only the high-angle optical receiver is treated as a crystal defect, while the foreign material detected from the certain area of the wafer by the low-angle optical receiver is treated as an attached foreign material.
Patent Document 2 discloses an apparatus for inspecting the surface of a wafer. The apparatus described in Patent Document 2 has a detector. Light scattered from an edge portion of the wafer has high directivity and is distributed in a direction extending from the edge portion and parallel to a normal to the surface of the wafer. Light scattered from a defect (such as a foreign material) present on the edge portion of the wafer does not exhibit high directivity. A detector(s) detects the light scattered from the defect under the condition that one or more detection optical units are arranged in a direction(s) other than the direction extending from the edge portion and parallel to the normal to the surface of the wafer and do not receive the light scattered from the edge portion. Alternatively, the detector(s) detects the light scattered from the defect, while a space filter(s) arranged on a Fourier transform surface(s) of the one or more detection optical units shields the light scattered from the edge portion.
Patent Document 3 discloses an apparatus for inspecting the surface of an object that is to be inspected. The apparatus described in Patent Document 3 irradiates and scans the surface of the object with a light beam to detect light scattered from the object. The apparatus has a position detection unit for detecting the relative position of the object to the position of a spot of the light beam. The apparatus also includes one of the following: a light shielding unit for preventing the scattered light from being incident on a detector for detecting the scattered light before the spot of the light beam detected by the position detection unit reaches an edge portion of the object; an optical path shielding mechanism for shielding the light beam on an optical path of the light beam before the spot of the light beam detected by the position detection unit reaches the edge portion of the object; and a controller for stopping a function of the detector for detecting the scattered light before the spot of the light beam detected by the position detection unit reaches the edge portion of the object. The apparatus reduces degradation of the detector due to the scattered light. In addition, Patent Document 3 describes that when the light beam reaches the edge portion of the object, the apparatus scans the object with the light beam to prevent an increase in the amount of the light scattered toward the detector from the edge portion.
In a process for manufacturing a semiconductor substrate or the like, a portion of the substrate, which is located near an outer circumferential edge portion (hereinafter referred to as an edge portion) of the substrate, may easily have a defect such as peeling. It is, therefore, necessary to inspect the defect present on the edge portion of the substrate and deal with the defect present on the edge portion early or in advance. A challenge is to maximize the total area of a chip(s) that is included in the total area of the substrate and can be used as a good product(s) and thereby to improve the yield of the product(s).
However, the defect inspection on the edge portion is not taken into account in Patent Document 1.
The apparatus described in Patent Document 2 may have a detection optical unit that does not receive light having high directivity and diffracted from the edge portion. Alternatively, the apparatus described in Patent Document 2 may be configured with the space filter that shields the light diffracted from the edge portion and having high directivity to prevent the detector from detecting the diffracted light. The apparatus described in Patent Document 3 prevents the scattered light (diffracted light) from being incident on the detector for detecting the scattered light, or shields the light beam on the optical path, or stops the function of the detector for detecting the scattered light, before the spot of the light beam detected by the position detection unit reaches the edge portion of the object. This prevents the light scattered (diffracted) from the edge portion from being detected.
However, Patent Documents 2 and 3 do not sufficiently take into account the inspection of a substrate portion located near the edge portion of the substrate at high speed and with high sensitivity.